Aquatic Rhythm Lab

Cycle your
first tank.

Every new aquarium goes through the same invisible process — bacteria slowly building up, ammonia and nitrite rising then falling, the water finding its balance. Choose your setup and watch it happen at your own pace.

AmmoniaFish waste breaks down into toxic ammonia — the cycle begins here
NitriteBacteria convert ammonia — nitrite rises before it falls
NitrateThe safer end product — removed with regular water changes
BacteriaThe colony that drives the cycle — needs time to establish
FishOptional from day one — higher stakes, closer attention needed

A simplified model for learning — real tanks vary. Use this to understand the process, not predict exact timelines.

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Set up your tank

Choose size, method, and plants — then run a fish-safe cycle at your own pace.

About this simulation

Every new aquarium goes through the same invisible process — bacteria slowly building up, ammonia and nitrite rising then falling, the water finding its balance. This simulator lets you watch that happen and make decisions along the way. No experience needed.

Tank size
🫙 Small Under 40L · Parameters swing faster · Less room for error
🪣 Medium 40–120L · More water volume · More forgiving of mistakes
🏊 Large 120L+ · Dilution helps enormously · Slower parameter swings
Cycling method
🧪 Fishless Add ammonia without fish · Bacteria grow safely · Easier to manage
🐠 Fish-in Fish in the tank from the start · Need feeding · Higher stakes

Fishless cycling is the gentler option. You add ammonia to feed the bacteria — no fish involved. The bacteria grow at their own pace, and when the cycle is done, the tank is ready for fish.

Starting plants?
🌿 Yes Absorbs nitrate · Adds oxygen · Competes with algae
— No plants Simpler setup · Nitrate accumulates faster

With a small tank, fishless cycling, and plants — expect the cycle to complete in roughly 3–4 weeks. Ammonia will peak first, then nitrite, then both will fall as bacteria establish. Plants will help keep nitrate manageable.

Inside the simulator

Three equipment toggles — heater, filter, and light — are on by default. Try turning one off to see what happens. There is a one-time bacteria starter (Seed). Use Status / Log on mobile to switch between guidance and the day-by-day log.

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Before you begin

Essentials below — details inside the guide.

One simulated day every 8 seconds. Pause, read the log, and use +1d when you want time to jump ahead.

Full guide — controls & rules
Time

Let it run. The log explains what is happening as it unfolds.

Equipment

Heater, filter, and light are on by default. Tap any of them to toggle off — and see what actually happens to the cycle.

Fish-in only

Feed every 1–2 days. After 4 days without food fish begin to weaken — stressed fish are less tolerant of ammonia.

Bacteria starter

Seed works once. Use it after a few days — bacteria need some ammonia present first before seeding helps.

Pause and skip

Pause to read carefully. Use +1d in the top bar to skip forward one day when you are waiting.

What you are trying to do

Get ammonia and nitrite down to near zero — and keep them there for three days in a row. That means your bacteria colony is mature enough to process waste continuously. You will see Stable ✓ in the bacteria panel when the cycle is complete.

The cycle crashes if ammonia or nitrite stays too high for too long — or if fish go without food. There is no time limit. The biology moves at its own pace.

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The cycle crashed.

Simulation report
Reflection & coaching
Next best action

Take the stable settings from this simulation, then use the same setup on your real tank for 7 days (feeding, water changes, and a consistent lighting schedule).

Apply this to real tank → Back to tools
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Day 1 Setting up
Ammonia ppm 0.00
Nitrite ppm 0.00
Nitrate ppm 0.00
Fish 0
Plants 0
Setting up...
NH₃0.00
NO₂0.00
NO₃0.00
🐠0
🌿0
What is happeningYour tank is ready. The cycle will begin when you add an ammonia source.
Day 1Tank set up. Ready to begin cycling.